Estimated Effects of Pumping on Groundwater Storage and Walker River Stream Efficiencies in Smith and Mason Valleys, West-Central Nevada

Scientific Investigations Report 2022-5123
Prepared in cooperation with the Bureau of Reclamation and U.S. Bureau of Indian Affairs
By:  and 



The Walker River originates in the Sierra Nevada Mountains and flows nearly 160 miles to its terminus at Walker Lake in west-central Nevada. The river provides a source of irrigation water for tens of thousands of acres of agricultural lands in California and Nevada and is the principal source of inflow to Walker Lake. Extraction of groundwater for agricultural use became prevalent in the late 1950s and early 1960s to supplement irrigation demands not met by surface-water diversions during times of drought. There is growing concern that continued groundwater withdrawals within the Walker River Basin are likely contributing to depleted streamflow of the Walker River and the long-term depletion of groundwater storage in the basin. This report documents changes in groundwater storage-volume and trends in Walker River stream efficiency, a measure of change in flow due to gaining or losing conditions, in the two largest agricultural valleys in the Walker River Basin, Smith and Mason Valleys, for a multi-decade period. Groundwater-level maps from previous studies were used for the beginning (1970) and middle (2006) points of this study. Groundwater levels measured from 1991–95 and 2016–20 were used to construct median groundwater-level maps that represented conditions in 1995 and 2020. Valley wide groundwater-level change was calculated by comparing groundwater-level maps for the periods 1970–95, 1996–2006, and 2007–20 and by observing the overall change from 1970 to 2020. Groundwater storage-volume change was calculated using groundwater-level change and previously defined specific yield values. Between 1970 and 2020, groundwater storage-volume declined 287,600 acre-feet in Smith Valley and 269,000 acre-feet in Mason Valley. Using groundwater storage-volume decline and annual groundwater pumpage rates, a maximum groundwater pumpage rate can be computed to support management of water resources. In Smith Valley, groundwater pumping in excess of 22,300 acre-feet per year would likely result in groundwater storage decline. In Mason Valley, groundwater pumping in excess of 75,200 acre-feet per year would likely result in groundwater storage decline. Stream efficiency was calculated using continuous streamflow data and monthly diversion volumes on two reaches: (1) the West Walker River in Smith Valley, from 1948 to 2020 and (2) the Walker River in Mason Valley, from 1958 to 2020. Stream efficiency during non-irrigation season in Smith and Mason Valleys declined at a statistically significant rate of 1.1 and 0.6 percent per year, respectively. Trends in stream efficiency corresponded to occurrence of prolonged drought, deviation from average annual streamflows, and total groundwater pumpage. Long-term declines in groundwater storage-volume and stream efficiency demonstrate that the alluvial aquifer system is becoming increasingly depleted, such that the river can no longer replenish groundwater storage while simultaneously balancing groundwater and surface-water withdrawals. The introduction of supplemental groundwater pumpage was intended to offset surface-water deficits during dry years; however, pumpage occurs even in years when average or above average streamflows meet surface-water demands. Reliance on supplemental groundwater pumpage has resulted in widespread groundwater storage-volume decline and decreased stream efficiency. With each successive drought cycle, the ability of Walker River to sustain streamflows and convey water downstream has diminished. Above average wet periods have a marginal and short-lived effect on rebounding the groundwater levels outside of the river corridor. Moreover, if the trend continues, each future drought cycle may further reduce groundwater supplies and that may further decrease streamflow reliability.

Suggested Citation

Davies, G.E., and Naranjo, R.C., 2022, Estimated effects of pumping on groundwater storage and Walker River stream efficiencies in Smith and Mason Valleys, west-central Nevada: U.S. Geological Survey Scientific Investigations Report 2022–5123, 49 p.,

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Abstract
  • Introduction
  • Methods
  • Results and Discussion
  • Summary
  • References Cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Estimated effects of pumping on groundwater storage and Walker River stream efficiencies in Smith and Mason Valleys, west-central Nevada
Series title Scientific Investigations Report
Series number 2022-5123
DOI 10.3133/sir20225123
Year Published 2022
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Nevada Water Science Center
Description Report: viii, 49 p.; Data Release: 4
Country United States
State Nevada
Other Geospatial Smith Valley, Walker Valley
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details